Production of artificial teeth



April 8, 1941. H HQLLMANN 2,237,350

PRODUCTION OF ARTIFICIAL TEETH Filed June 4, 193a Jawnfar HEINRICH H01.LMA/VN SFZ Z 5% Him/wags Patented Apr. 8, 1941 entree STATES PATENTQFFICE Application June 4, 1938, Serial No. 211,741 In Germany June 11,1937 1 Claim.

In order to simplify the production of artificial teeth, it has longbeen the practice to standardize them. The first steps in thisstandardization process were the Logan and Davis crowns, but these werenot successful, owing to the fact that there was too great a disparitybetween the metal cap or superstructure of the root pin and theporcelain crown, Attempts have been made to eradicate this defect bymodifying more or less the cavity in the crown and the caps of the rootpins so as to achieve greater strength and a better hold. All thesetypes of crowns had the common feature that they enabled the face of thecrown to be adapted to the face of the root by suitable means, afterwhich the cap or super structure could be cast onto the root pin in thelaboratory. Since, however, by far the greater proportion of practisingdentists, about 95% do not possess their own laboratories, this methodof preparing a porcelain crown demanded greater expenditure of time andmoney. To overcome this disadvantage the industry adopted the course ofputting on the market ready-made root pins with their caps more or lessshaped to fit the cavities in the crowns. But as the incisor and eyeteeth that came into question chiefly necessitate far more than ahundred different sizes, a corresponding number of pins would naturallyhave had to be available, with their ready-made caps corresponding withthe sockets of the crowns.

This would have necessitated the stocking of an impracticable number oftwo parts, and therefore, the sizes of crown were subdivided into groupsaccording to their cavities and for each such group root pins wereprovided, with caps or superstructures shaped in accordance with thecavities of the crowns. The dentist thus had the task on the one hand offirst finding a pin that was adapted, as far as its superstructure wasconcerned, to the tooth to be substituted, and on the other hand, whenhe had found this, of looking for the crown fitting this superstructure.Thus the dentist was obliged to keep a large stock of crowns and rootpins and caps always available.

It is the object of the present invention to solve this problem, andthis is achieved essentially by means of an intermediate element adaptedto the crown cavity and the root pin cap or superstructure. The toothstructure according to the invention is built up with the followingmeans and in the following manner:

(a) A root pin that is adapted to be inserted and afiixed in the root inany manner, but with a cap that is the same for all teeth.

(b) An intermediate element interposed between the root pin and crown,the cavity of which is shaped to correspond to the cap of the root pinand which, like the latter, is always the same for all teeth, whilst itsexternal dimensions are varied according to the different sizes of teethor the different dimensions of the cavities of the teeth, the teeth andintermediate elements tallyingwith one another in their internal orexternal dimensions being first of all assembled loosely;

(c) The crown is fitted to the face surface of the root, for example, bygrinding;

(d) The individual parts are attached together, for example, bycementing.

With such a construction it is possible to make the intermediate elementof porcelain and to adapt its colour to that of the tooth, and, further,(for facilitating the fitting together of the face surfaces of the crownand root) to utilize an auxiliary check plate shaped in accordance withthe support surface that is required.

Further features of the invention concerning the external formation ofthe intermediate element and its anchoring to the superstructure of theroot pin, will be described hereinafter.

Advantages afforded by the invention include simplification of themake-up and assembly of the artificial tooth, with a considerable savingof time, substantial reduction in the number of pins and crowns requiredto be stocked, with a consequential cheapening of the teeth,independence on a laboratory owing to the fact that the intermediateelement enables an individual crown to be made without it first beingnecessary, as was previously the case, to prep-are the necessarysuperstructure or cap in the laboratory and then to burn an individualcrown thereonto.

To facilitate understanding of the present invention, I have appendedhereto a sheet of drawings in which the invention is illustrated by wayof example and in which:

Fig. 1 is a longitudinal section through an artificial tooth constructedaccording to the invention,

Fig. 2 is a side elevation illustrating a check plate for use inadapting the crown to the root,

Fig. 3 is a view illustrating the manner in which the intermediateelement in Fig. 1 is applied to the root pin cap, and

Fig. 4 illustrates a modified formation of intermediate element and rootpin cap.

Referring to Fig. 1, a is the root of the tooth, b the tooth crown and cthe root pin, which can, of course, be of any other form. The root pin 0is provided with a fixed cap or superstructure d, which is the same forall teeth. Over this cap d an intermediate element e of any suitablematerial is disposed, the cavity of such element being shaped tocorrespond to the cap 11 of the root pin and being, like the latter, thesame for all teeth, whilst its outer dimensions are varied according tothe different sizes of teeth or the different dimensions of the cavitiesof these teeth. Each tooth b is fitted with the intermediate element efrom the outset, although at first only loosely, the parts beingcomplementary to one another in their internal and external dimensionsrespectively and constituting what may be termed a crown unit. In theexamples illustrated in the drawing the intermediate element c has ashoulder ,f on which the crown b is supported by a corresponding recess,thus giving a high resistance to the masticating pressure.

On the root pin cap d and in the interior of the intermediate element erecesses are made which form ledges or tongues g, h spaced apart oneabove the other. When the space 1' between the element 8 and the cap 01is filled with cement the ledges or tongues g, h co-operate with thecement and set up a firm anchorage between the pin cap d and theintermediate element 6. The distance between the tongues g, 71. (thatis, the size of the recess 1), is made such that the element 8 can befitted over the pin cap at, this procedure being assisted by therearward bevelled surface k, inasmuch as when the intermediate element 6is being applied and is in an oblique position its inner edge I slidespast the outer edge m of the root pin cap d (Fig. 3)

The artificial tooth according to the present invention is built up inthe following way: After removing the rest of the old crown and fittingthe pin bed into the root, the face of the root is ground, using thecheck plate illustrated in Fig. 2, the shape of which correspondsexactly to the base face of the crown that is to be inserted. The faceof the root is corrected until the plate n lies absolutely evenlythereon. Any

differences between the faces of the root and crown are then removed onthe crown face. By means of this check plate n, which is fixedly orreleasably connected to an auxiliary root pin and is guided by a handle0, the grinding of the crown face is reduced to a minimum, whichundoubtedly means simplification and saving of time for the dentist.

The root pin is then cemented in, the intermediate element is anchoredto the root pin cap, and the crown is cemented to the intermediateelement.

In the example selected the cap d and the intermediate element 6 aremade non-circular in order to simplify assembly of the individual partsto one another and to make such assembly secure.

The example according to Fig. 4 differs from that of Figs. 1 and 3 bythe fact that the root pin cap d has on its top surface a channel-likerecess p which is engaged on assembly of the parts by a rib q providedin the interior of the intermediate element 6, whereby a statically morefavourable effect is achieved.

I claim:

An artificial tooth comprising a root pin of standard size andconstruction, a cap of standard size and construction integral with saidroot pin, an outwardly projecting tongue on said cap, a hollowintermediate element mounted on said cap, the cavity formation of saidelement being standard but its external formation varying according tothe size and type of the crown, an inwardly projecting tongue in thecavity of said hollow element adapted to co-operate with the tongue onsaid cap to anchor the parts together when cement is introduced,crown-supporting shoulders on the exterior of said intermediate element,and a socketed crown whose socket formation corresponds to the externalformation of the intermediate element.

HEINRICH HOLLMANN.

